1. Field of Invention
The present disclosure relates to downhole pumping systems submersible in well bore fluids. More specifically, the present disclosure concerns preventing rotation of stators in an electrical submersible pump with mechanical anchoring.
2. Description of Prior Art
Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the wellbore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs an electrical submersible pump (ESP). ESPs are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via a power cable. ESPs usually are made up of a pump motor at its lowermost section with a seal section adjacent the pump motor. The seal section is used for equalizing pump system internal pressure with ambient to minimize the pressure differential across the pump system seals.
Motors for electrical submersible pump systems are typically formed by stacking a series of annular stator laminations inside a pump motor housing. Grooves are normally formed within the housing at the top and bottom terminal ends of a lamination stack. The grooves are configured to receive a snap ring, where the snap ring inner diameter extends into the pump motor from the housing inner diameter. Forming the motor typically comprises inserting the snap ring located at the bottom of the housing, then adding the lamination stack within the housing. The laminations are then compressed, with a press or some other mechanical device; while the laminations are still under compression the top snap ring is inserted. After the pressure on the lamination stack is released, the stack will slightly spring back and exert an axial force on both top and bottom snap rings, where the opposing force is in opposite directions. This force on the snap rings will slightly stretch the housing along its length to create an axial force intended to prevent lamination spin during motor operation.
The ESP pump motors also comprise a rotor attached to a pump motor shaft. The rotor also consists of corresponding rotor laminations usually coaxially within. The stator lamination stack and the rotor lamination stack include openings that axially run along the length of the motor, wherein the openings contain wires, or other electrical conducting elements that form corresponding coils in each of the rotor and stator lamination stack. Typically the coil in the stator lamination stack is energized to form an electrical field that through electromagnetic forces produces a rotation in the rotor stack and thus correspondingly rotates the pump motor shaft.